Feedback From the Environment

My Question and Answer
Q: Is the skin a sensory structure?
A: YES. Sensory receptors found in skin include mechanoreceptors, thermoreceptors, and pain receptors (nociceptors).They help the organism feel touch, temperature, and pain. For example, free nerve endings detect heat, light pressure, and pain. Pacinian corpuscles feel firm pressure. Meissner corpuscles feel continued light pressure. Ruffini endings sense continuous pressure.


1. What particular sensory structures does the organism have? What advantage exists for that specific structure? Are there similarities to structures found in the other organisms?

• Pig
  • Sensory structures of the pig include the eyes, ears, mouth, nose, and facial hairs. The eyes have a nictitating membrane, which is a mass of tissue in the corner, that helps keep the eye clean. Birds also have this. The ears have a flexible outer flap called the pinna. The pinna helps the pig hear by focusing the sound. In the mouth, the big has 44 teeth used for grinding food found in the environment. Many herbivores have teeth like this. Ancient plant-eating dinosaurs had flat teeth like this for grinding food, as well. The pig has a long snout it uses for smell to find food. The aardvark has a longer snout, but is used for the same thing. Lastly, sensory facial hairs called vibrissae help the adult pigs find their way in the dark. These are common in many mammals.
• Crayfish
  • Crayfish have compound eyes to help them see as well as antennae in which they use to sense changes in water pressure. All arthropods have compound eyes, and many of them have antennae as well.
• Starfish
  • Starfish have chemoreceptors all over their bodies. They detect levels of carbon dioxide in areas. Also, they have tube feet to help them move and eye spots to sense light and dark.

2. How has evolution been part of their survival?

• Pig
  • It is said that pigs have evolved from wild boars. Through time, pigs have evolved to develop more elongated teeth. They have also gotten bigger --- pigs used to be very small creatures, and wild boars would eat the smaller pigs. They have developed a more acute sense of smell, as well.
• Crayfish
  • Through time, crayfish have been able to adjust to different waters. They have also developed thicker outer shells and strong claws. Their stomachs are located in the center of them.
• Starfish
  • Starfish have been around for a very long time. They vary in shapes and sizes. Through evolution, starfish have gained the ability to grow back a broken limb. This is called regeneration. It is necessary for survival, for their limbs are very fragile.

3. Follow the taxonomy of each of the organisms from kingdom to species.

• Pig:
  • Kingdom - Animalia
  • Phylum - Chordata
  • Class - Mammalia
  • Subclass - Theria
  • Infraclass - Eutheria
  • Order - Artiodactyla
  • Family - Suidae
  • Subfamily - Suidae
  • Genus - Sus
• Crayfish
  • Kingdom - Animalia
  • Phylum - Arthropoda
  • Subphylum - Crustacea
  • Class - Malacostraca
  • Order - Decapoda
  • Suborder - Pleocyemata
  • Infraorder - Astacidea
  • Superfamily - Astacoidia
• Starfish
  • Kingdom - Animalia
  • Phylum - Echinodermata
  • Subphylum - Asterozoa
  • Class - Asteroidea
  • Order - Forcipulatida
  • Family - Asteriidae
  • Genus - Asterias
  • Species - Rubens

4. What are their cousins? What is one of their past ancestors (extinct) of which they share something in common?

• Pig
  • Cousins of the pig include wart hogs, guinea pigs, and wild boars. One extinct ancestor of the pig is the daedon, a prehistoric pig that also resembled a rhinocerous. They have many common structures including the snout, feet, and tail.
• Crayfish
  • Cousins of the crayfish include lobsters, crabs, shrimp, and shellfish. An extinct cousin is the trilobite. They have the same type of outer shell in all crustaceans.
• Starfish
  • Cousins of the starfish include the sea urchin, brittlestars, crinoids, and sea cucumbers. An extinct ancestor is the asteroid, which has radial symmetry and several common sensory structures.

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